Various design parameters affect the performance of a wood-type golf club (e.g., drivers, fairway woods, and hybrids). Accordingly, golf equipment designers are constantly manipulating the shape, size, and materials used to manufacture clubs and balls.
For example, as golf club heads have increased in volume, their moments of inertia have also increased. Indeed, a larger moment of inertia, which is the resistance to twisting of any golf club head when the golf ball is impacted off center, provides what manufacturers refer to a “larger sweet spot” and results in more forgiveness on off-center hits. However, when the volume of a golf club head is maximized through spatially distributing the mass in all three orthogonal orientations, the center of gravity of the golf club head is positioned substantially rearward from the front face of the golf club head, which renders shots struck off-center from the sweet spot of the golf club head undesirable as a result of the side-spin or backspin.
In some instances, one or more weight members attached to the golf club head may be positioned to manipulate the center of gravity. Alternately, manufacturers have attempted to manipulate the distribution of the amount of material in various parts of the head to strike a balance between the moment of inertia and center of gravity. Adding weight to certain areas of a golf club head, however, may cause it to become heavy and unwieldy, possibly to the point of limiting a golfer's swing speed and adversely affecting the golfer's swing mechanics. Similarly, manipulating the distribution of material may result in a club head that cannot withstand the stress of repeated impacts with a golf ball that occur during normal use of the resulting golf club.
Designers have also attempted to manipulate the weight distribution of the club head using low and high density materials, although low density materials are typically only been placed in non-critical areas or low impact areas. In addition, attempts to manipulate the weight distribution of the club head using low and high density materials are somewhat limited by the process, e.g., the thickness/thinness of the casting. For example, a widely used material for wood-type golf club heads is titanium alloy. The alloy is available for casting and in wrought sheet form, but because the mechanical properties of the cast material are inferior to the wrought material, the thickness of the cast material must be greater than the wrought material for maximum performance. Accordingly, the weight reduction in non-critical areas of the club head is limited to the thickness/thinness that can be achieved with the specific material used and the casting process rather than the mechanical properties of the alloy material.
With regard to fairway woods, which have a smaller profile than drivers but larger profile than hybrids, if conventional titanium alloys are used to make the fairway wood golf club head, the low density of the material requires additional weights to be added to meet the required mass. Thus, most manufacturers use stainless steel for the body and titanium for the face. However, this is not ideal because the combination of materials yields two discrete densities and limits the design options.
Therefore, there is a continuing need for wood-type golf club heads (and methods of manufacturing such heads) that have high strength faces and bodies made from metal alloys with densities that can be tailored depending on the shape, size, and performance requirements of the particular club head. Accordingly, the present invention provides a method of making a golf club head (and the resulting golf club head) that includes multiple materials to achieve the proper balance between mass distribution and club head performance.